Octanol/water partition coefficients for environmentally important organic compounds : Test of three RP-HPLC-methods and new experimental results.

Partition coefficients PO,w ((i)) describing the distribution of a solute i onto coexisting phases of 1-octanol and water are needed in a large variety of applications. They can be measured directly by HPLC as long as log PO,w ((i))≧ 3.5. For more hydrophobic substances, several experimental procedures have been proposed in the literature. The reliability of those methods is questionable. Therefore, in the present work, PO,w ((i)) is determined experimentally by three HPLC methods using reversed-phase HPLC [1]. Results from different procedures are compared critically. The method of Braumann [2] proved to be superior over the OECD-guidelines [3]. It was therefore applied to determine octanol/water partition coefficients for 23 substances at 25 °C. For eight of those substances (4-methylindole; 9-(hydroxymethyl)anthracene; N-ethylcarbazol; ethylcyclohexane; trans-2-octene; l,l-dimethyl-(ethy])cyclohexane; heptylbenzene; 4-dodecyl-l,3-benzenediol) no experimentally determined number for PO,w ((i)) has been published before.